Investigating multisensory convergence in the auditory cortex

Andrew King, Department of Physiology, Anatomy and Genetics, University of Oxford

Abstract
Multisensory convergence is now known to be extremely widespread within the brain, extending well beyond areas such as the superior colliculus and association areas of the cortex. Indeed, the prevalence of crossmodal interactions reported in recent studies in humans and other species suggests that most of the cerebral cortex is multisensory in nature. Particular attention has focussed on the auditory cortex where inputs from other sensory modalities have been found in both primary and non-primary fields. Multisensory integration has so far been defined only in terms of enhancement and suppression of neural responses. This is surprising given the importance of temporal coding and we have found that measures which take into account the full spike discharge pattern provide a more sensitive index of multisensory convergence than those based on spike rate alone. Although the integration of facial and vocal signals in primate auditory cortex is clearly important for communication, the functional significance of the multisensory responses described in most studies, which typically use much simpler stimuli, is poorly understood. Valuable insights into those functions and of the role of different auditory cortical fields can be obtained, however, by studying not only the receptive field properties of the neurons but also the sources of their non-auditory inputs.

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